Not to contradict Buffalo Gal (who is a very wise woman indeed), I have to say, I think it depends on the individual farm. Some farms have more of a Cocci load than others, and I think that makes a difference as to whether you should use medicated feed.
I always use a medicated Turkey starter for my Buckeye chicks, for at least the first few weeks. I cut it with a medicated chick starter to bring the protein down to about 20%, and then slowly switch them over to the 18% feed I use for my adult birds at about 8 weeks.
I used to not use medicated feed and had unacceptable losses from Cocci. I think it all depends on where you are and whether or not the protazoa is in the soil. Sulmet is ok, but it didn't work well enough for me. So I went with a medicated feed for the chicks.
Also, I used to vaccinate for Marek's, and I found I wasn't having a lot of trouble with it, so I stopped. But some folks do have trouble with it, so for the first time I am offering it to my customers this year, at just the cost of the vaccine (no additional charge for my time.) It's not cheap though, $35.45 for the vaccine and the shipping!